Abnormalities in gene expression constitute the underlying defect in hereditary diseases such as the thalassemia syndromes, and are likey to play a role in the causation of cancer and many other disease states. This project is aimed at elucidating the interactions between DNA and nucleoprotein structure which regulate the expression of globin genes during avian erythroid differentiation. The avian arythroid model offers several technical advantages for such studies of DNA structure and DNA-protein interactions because of the availability of pure populations of developmentally-specific erythroid cells and nuclei. The studies proposed here will examine the regulation of avian globin genes at various functional levels including: 1) in an animal model; 2) in cultured cell transient-expression transcription assays; 3) in long term culture cell transformation assays; and 4) in defined in vitro transcriptional assays of modified and unmodified globin genes. This comprehensive approach should help clarify the relatioship between precise molecular control mechanisms determined in highly defined biochemical assays and those functionally important controls which operate in intact erythroid tissues. The proposed studies are made possible by the availability of: 1) well-characterized recombinant clones containing the chicken Beta-type globin genes; 2) whole cell and cell free transcriptional assays to test the effect of DNA methylation and specific sequences upon globin gene expression; and 3) a recently developed animal model in which embryonic globin gene expression can be reactivated by pharmacologic manipulation with 5-azacytidine and sodium butyrate. The long term goal of this research project is to elucidate the basic mechanisms of control of cellular differentiation at the level of gene expression and to determine their functional significance. This knowledge should be directly applicable to hereditary diseases such as thalassemia and sickle cell anemia in which the underlying defect is known to be abnormal globin gene expression, and in which the ability to manipulate globin gene expression could lead to correction of these disease states. In addition, an understanding of the molecular controls involved in gene regulation and cellular differentiation should ultimately allow a better understanding and treatment of many other types of hereditary disorders as well as cancer.